When traceSiblingValue() encounters a PHI-def value created by live
range splitting, don't look at all the predecessor blocks.  That can be
very expensive in a complicated CFG.

Instead, consider that all the non-PHI defs jointly dominate all the
PHI-defs.  Tracing directly to all the non-PHI defs is much faster that
zipping around in the CFG when there are many PHIs with many
predecessors.

This significantly improves compile time for indirectbr interpreters.

llvm-svn: 139797

In some cases such as interpreters using indirectbr, the CFG can be very
complicated, and live range splitting may be forced to insert a large
number of phi-defs.  When that happens, traceSiblingValue can spend a
lot of time zipping around in the CFG looking for defs and reloads.

This patch causes more information to be cached in SibValues, and the
cached values are used to terminate searches early.  This speeds up
spilling by 20x in one interpreter test case.  For more typical code,
this is just a 10% speedup of spilling.

The previous version had bugs that caused miscompilations. They have
been fixed.

llvm-svn: 139378

It broke the self host and clang-x86_64-darwin10-RA.

llvm-svn: 139259

In some cases such as interpreters using indirectbr, the CFG can be very
complicated, and live range splitting may be forced to insert a large
number of phi-defs.  When that happens, traceSiblingValue can spend a
lot of time zipping around in the CFG looking for defs and reloads.

This patch causes more information to be cached in SibValues, and the
cached values are used to terminate searches early.  This speeds up
spilling by 20x in one interpreter test case.  For more typical code,
this is just a 10% speedup of spilling.

llvm-svn: 139247

The problem is fixed for all register allocators by r138944, so this
patch is no longer necessary.

<rdar://problem/10032939>

llvm-svn: 138945

I don't currently have a good testcase for this; will try to get one
tomorrow.  <rdar://problem/10032939>

llvm-svn: 138794

When trying to rematerialize a value before an instruction that has an
early-clobber redefine of the virtual register, make sure to look up the
correct value number.

Early-clobber defs are moved one slot back, so getBaseIndex is needed to
find the used value number.

Bugpoint was unable to reduce the test case for this, see PR10388.

llvm-svn: 135378

Spills should be hoisted out of loops, but we don't want to hoist them
to dominating blocks at the same loop depth. That could cause the spills
to be executed more often.

llvm-svn: 134782

Try to move spills as early as possible in their basic block. This can
help eliminate interferences by shortening the live range being
spilled.

This fixes PR10221.

llvm-svn: 134776

Remat during spilling triggers dead code elimination. If a phi-def
becomes unused, that may also cause live ranges to split into separate
connected components.

This type of splitting is different from normal live range splitting. In
particular, there may not be a common original interval.

When the split range is its own original, make sure that the new
siblings are also their own originals. The range being split cannot be
used as an original since it doesn't cover the new siblings.

llvm-svn: 134413

llvm-svn: 134189

about to be spilled.

This can only happen when two extra snippet registers are included in the spill,
and there is a copy between them. Hoisting the spill creates problems because
the hoist will mark the copy for later dead code elimination, and spilling the
second register will turn the copy into a spill.

<rdar://problem/9420853>

llvm-svn: 131192

llvm-svn: 130931

This could happen when trying to use a value that had been eliminated after dead
code elimination and folding loads.

llvm-svn: 130597

llvm-svn: 129883

the spilled register.

This is quite common on ARM now that some stores have early-clobber defines.

llvm-svn: 129714

The rematerialized instruction may require a more constrained register class
than the register being spilled. In the test case, the spilled register has been
inflated to the DPR register class, but we are rematerializing a load of the
ssub_0 sub-register which only exists for DPR_VFP2 registers.

The register class is reinflated after spilling, so the conservative choice is
only temporary.

llvm-svn: 128610

The spill weight is not recomputed for an unspillable register - it stays infinite.

llvm-svn: 128490

llvm-svn: 128469

This may eliminate some uses of the spilled registers, and we don't want to
insert reloads for that.

llvm-svn: 128468

The instruction to be rematerialized may not be the one defining the register
that is being spilled. The traceSiblingValue() function sees through sibling
copies to find the remat candidate.

llvm-svn: 128449

The main register class may have been inflated by live range splitting, so that
register class is not necessarily valid for the snippet instructions.

Use the original register class for the stack slot interval.

llvm-svn: 128351

This can happen when multiple sibling registers are spilled after live range
splitting.

llvm-svn: 127965

llvm-svn: 127964

llvm-svn: 127959

Stack slot real estate is virtually free compared to registers, so it is
advantageous to spill earlier even though the same value is now kept in both a
register and a stack slot.

Also eliminate redundant spills by extending the stack slot live range
underneath reloaded registers.

This can trigger a dead code elimination, removing copies and even reloads that
were only feeding spills.

llvm-svn: 127868

I have convinced myself that it can only happen when a phi value dies. When it
happens, allocate new virtual registers for the components.

llvm-svn: 127827

After live range splitting, an original value may be available in multiple
registers. Tracing back through the registers containing the same value, find
the best place to insert a spill, determine if the value has already been
spilled, or discover a reaching def that may be rematerialized.

This is only the analysis part. The information is not used for anything yet.

llvm-svn: 127698

Remove the unused reserved_ bit vector, no functional change intended.

This doesn't break 'svn blame', this file really is all my fault.

llvm-svn: 127607

This allows the allocator to free any resources used by the virtual register,
including physical register assignments.

llvm-svn: 127560

llvm-svn: 127530

Live range splitting can create a number of small live ranges containing only a
single real use. Spill these small live ranges along with the large range they
are connected to with copies. This enables memory operand folding and maximizes
the spill to fill distance.

Work in progress with known bugs.

llvm-svn: 127529

This makes it possible to register delegates and get callbacks when the spiller
edits live ranges.

llvm-svn: 127389

llvm-svn: 127388

This will we used for keeping register allocator data structures up to date
while LiveRangeEdit is trimming live intervals.

llvm-svn: 127300

llvm-svn: 127181

register.

This avoids some silly stack slot shuffling when both sides of a copy get
spilled.

llvm-svn: 126353

llvm-svn: 126258

This almost guarantees that the COPY will be coalesced.

llvm-svn: 125140

The target hook doesn't know how to do that. (Neither do I).

llvm-svn: 125108